I dont have a codeplug for cardiff , but I can tell you that most of the "interesting" traffic will not be
readable on an MD380.

The central store and pub network (charlie romeo) in the centre uses TETRA (different digital mode) that the MD380 wont pick up
A lot of the council services (highways, telecare, viridor binmen etc) have moved onto a DMR TIER3 system
which has a feature called RAS (restricted access to system) which the MD380 cannot read. The same is true of
Cardiff castle. parts of the millenium stadium use TETRA too.

Thats not to say theres nothing to listen to - there is! but you'll need to hunt it The MD380 is a great radio (
I have 4 here and an MD9600) but its a limited digital scanner, and not a hunting tool

Do you have a regular scanner with a discriminator tap or an RTL-SDR with SDR# software and a copy of DSD+ ?
You're going to need those to find the DMR signals initially, then once the 4 parameters for each channel are known to you
(frequency, timeslot, colour code, talkgroups in use) you can use those fields to programme your MD380. if you load the
3rd party firmware it adds an additional mode called "promiscuous" which reduces the list to 3 parameters and if you use
one particular version (ty toolz) you get a colour code scanner as well.

but bear in mind that your MD380 can only give you direct access to 16 channels at a time, and can only scan 30 at a time.

Sorry if this sounds like bad news but I thought it best to "tell it like it is" . If you're looking for a "turnkey" solution for DMR scanning
I'm afraid its sell the MD380 and invest in a whistler / uniden 3600.

Couple of known DMRs to start you off if you have the md380toolz with the colour code scanner (I'm not going to share colour codes,
and talkgroups anymore via a web forum due to experiences with various d***heads - no names/ packdrill)